For those in the South interested in Drainage Water Management (DWM) systems, the focus is normally on irrigation. But the system — sometimes called subsurface irrigation — also helps with nutrient loss and increased yields.

Here’s the idea: pipes placed underground — in conjunction with water control structures in tile lines — allow excess water to be removed from ground under the crop. “Stop logs” are then placed, or removed, from the structures depending on how much, or how little, water a farmer wants on his land.

“Right now, in our area there’s still interest in tiling,” says John Hester, an NRCS engineer in the Missouri Bootheel. “People are calling and asking questions. The trouble they’re having, right now — and this is pretty much happening in all sectors of agriculture — is commodity prices are making it prohibitive to jump into (installing such systems). So, people seem to be holding back a bit.”

Mark Nussbaum, also an NRCS engineer in the region, says, “We have a (system) going in today. But in terms of the big picture, these are very capital-intensive projects and a long-term investment. So, they’re holding out for better crop prices.”

Even so, Hester has “never seen anyone who’s put one in who’s been disappointed.”

Nussbaum references a YouTube video on the DWM systems. “It shows how farmers can be extremely efficient with water use. If we’re going to surface irrigate a cornfield in this area, we’ll use 10 to 12 inches. To get the same yield increase using subsurface irrigation, it takes about 5 to 6 inches.”

The engineers work a region far enough into the South “where irrigation is key to making a good quality crop,” says Nussbaum. “The folks who made these videos were focused on water quality and the irrigation aspect was secondary. Farther north, they want drainage, but by the time we get to our region, irrigation is paramount.”

“That said, until one of these systems is installed farmers don’t realize how much drainage issues have been affecting their fields,” says Hester. “Once they install it, it makes a big difference in the spring with replants and other things.”

There’s no magic to it.

“The reason is with subsurface irrigation there’s essentially no surface evaporation. That’s a very big deal for some farmers. We’ve had visitors from California, where water access is limited, looking at this. There are farmers there now doing this.”

The men say there’s also been strong interest from farmers in central and southeastern Kansas, where there are concerns about water rights.

Consistency

“We say ‘high yield’ and when farmers plant a crop they’re aiming for that when fertilizing or anything else,” says Hester. “When you have good drainage in the field, you should consistently see very similar, higher yields. Without the drainage, sometimes plants don’t use the fertilizer as efficiently.

“If you’re adding fertilizer for corn and, boom, there’s an extended wet period while you need to plant soybeans” that can lead to a dilemma, says Nussbaum. “It can mean fertilizing incorrectly from a profit potential and from a water quality perspective. That happens more than we care to admit.”

There’s another issue linked with the predictability of DWM, says Nussbaum. “Farmers will say, ‘I may be looking at commodity prices two years out and see an opportunity to book corn. Well, with the DWM systems there’s a very high probability of being able to plant, harvest and sell that corn.’

“But with very wet soils there isn’t an opportunity to book corn two or three years out with the same assurance.” A farmer may run into “a very wet spring and have to shift from corn to soybeans. So, the DWM systems become a really important profit tool — being able to market in a long-term environment.”

Longevity

What about the longevity of these systems?

The very old tile systems had a lifespan of something like 20 or 30 years.

“Then, there was a shift to plastic pipe with holes about the size of your little finger,” says Nussbaum. “The lifespan then was determined by silt intrusion and they could last 40 years, or so.”

Since then, the drainage industry has “advanced by leaps and bounds. The most commonly installed product now has much less silt intrusion.”

The engineers started using the new systems in 2004. In 2016, one of the systems that had been built 10 years earlier was uncovered.

“We had to dig in to splice in a new pipe for an unrelated issue,” Nussbaum continues. “That gave us a great opportunity to see what the silt intrusion was. The net silt wasn’t zero but it was very close. So, after a decade, there was less than a 5 percent intrusion. That translates to a system longevity of well in excess of 40 years.”

Sharkey and quantity

One of the questions frequently put to the engineers is will DWM systems work in high-clay soils similar to Sharkey?

“That tends to be one of the tougher soils,” says Hester. “We’ve done work with that, and farmers who have experimented with it have found it works. The issue is always the cost because to make the system work in high clay soils the lines have to be very close.

“The key for successful sub-irrigation is you have to have wet soils. There has to be something holding that water up. If you’ve got a sandy soil and there’s good internal drainage, it’s very difficult to pump water back and hold it.”

The DWM systems are especially relevant “wherever there is a significant cost for water,” says Nussbaum. “Whenever that is the case, for whatever reason, the issue of water savings becomes very real and can be calculated. Where there are areas of water quantity issues, this is something to investigate.”

Regardless, if you’ve got a drainage problem, says Nussbaum, “come see the NRCS and we can help define it and help come up with solutions.”

Another DWM video to check out: https://www.youtube.com/watch?v=j4mYch4RFsY&t=178s.